Heat treatable coated glass

ABSTRACT

A heat-treatable coated glass article comprises a substantially transparent substrate with a substantially transparent dual-function coating on a surface of the substrate. The coating provides low emissivity and high anti-solar performance properties. It comprises a first anti-reflection layer of dielectric material, preferably tungsten oxide. An infra-red reflective layer of silver metal and/or copper metal overlies the anti-reflection dielectric layer. A buffer layer, such as a chromium buffer layer, is positioned between the anti-reflection layer and the infra-red reflective layer. Also, optionally, a color control layer may be used, preferably being positioned between the anti-reflection layer and the substrate. A second buffer layer directly overlies the infra-red reflective layer. A second anti-reflection layer overlies the second buffer layer. In accordance with a method of manufacturing the coated article, each of the layers of the coating is deposited in turn by D.C. magnetron sputtering in a multi-station sputtering chamber. Passing the transparent substrate through the sputtering chamber a second time to produce a double-layer coating structure is found to provide especially high quality performance characteristics.

INTRODUCTION

[0001] The present invention is directed to transparent substrateshaving multi-layer coatings for thermal insulation properties, as wellas to methods of manufacturing such multi-layer coated articles. Theinvention relates, in particular, to coated, transparent glasssubstrates which are heat treatable. Certain preferred embodiments aresuitable especially for automotive and architectural applications,exhibiting high visible light transmittance and high infra-red (IR)energy reflectance.

BACKGROUND

[0002] Coated glazing products having anti-solar properties, that is,low transmittance of wavelengths in the infra-red range, are known tothose skilled in the art. Coatings for glazing products are disclosed,for example, in European patent application 0 646 551 A1 entitledHeat-Treatment Convertible Coated Glass and Method of Converting Same.That document discloses silver coatings comprising a layer of Si₃N₄ overa layer of nickel or nichrome, over a layer of silver, over a secondlayer of nickel or nichrome, over a second layer of Si₃N₄. Sputtering isdisclosed for producing such coating. Sputtered deposition of amulti-layer coating is described, for example, in European PatentApplication 0,418,435 to Nalepka. The multi-layer coating of Hayward etal. is said to comprise a layer of sputtered zinc, tin, titanium,indium/tin or bismuth oxide, next a layer of sputtered silver or silveralloy, then a layer sputtered titanium or stainless steel and finally alayer of zinc, tin, titanium, indium/tin or bismuth oxide. Suchmulti-layer film is said to have excellent visible light transmissionwhile controlling both near infra-red solar energy and far infra-redreflected energy. A temperable coated article is suggested in U.S. Pat.No. 5,552,180 to Finley et al. The coated article of Finley et al.employs a metal-containing film such as titanium nitride whichordinarily oxidizes at the high temperatures encountered during glasstempering, along with an overcoating of a protective layer of a siliconcompound and an undercoating with a stabilizing metal-containing layer.In U.S. Pat. No. 3,990,784 to Gelber a multi-layer coating forarchitectural glass is suggested, comprising first and second metallayers with a dielectric layer disposed between them. Gelber suggeststhat the transmission properties of the coating can be changedindependent of its reflection properties, by varying the thickness ofthe metal layers while maintaining the ratio of their thicknessesconstant.

[0003] Similar coatings are disclosed in European Patent Application97104710.5 published as EP0796 825 A2, wherein a low emissivitysputtered coating employs controlled index of refraction of an undercoatlayer of an appropriate dielectric material below a first Si₃N₄ layer.Also a layer of silver is used, sandwiched between layers of nichrome.The term “nichrome” is used to designate a layer which includes somecombination of nickel and chromium, at least some of which is in itsmetallic state, although same may be oxidized. In a similar way, theterm “silver” means that the layer consists essentially of metallicsilver, but may include some other elements in small concentrations thatdo not adversely affect the performance characteristics of the silver inthe system as a whole. Bent or toughened silver coated glass is taughtin European Patent Application 87300601.9 published as No. 0233 003. Anadditional layer of aluminum, titanium, zinc, tantalum or zirconium isused over the silver layer, or both over and under the silver layer. Inrecent years, the popularity of coated glasses has occasioned numerousattempts to achieve a coated glass article which, prior toheat-treatment, can be coated, and which thereafter, can be heat-treatedwithout adversely changing the characteristics of the coating or theglass itself (i.e., the resulting glass article). One of the reasons forthis is, for example, that it can be extremely difficult to achieve auniform coating on an already bent piece of glass. It is well-known thatif a flat glass surface can be coated and thereafter bent, much simplertechniques can be used to get a uniform coating than if the glass hasbeen previously bent. This is true for architectural, automotive, andresidential glasses.

[0004] Various difficulties have been encountered by those skilled inthe art in developing commercially suitable coatings for architecturaland automotive glazing. In particular, it has proved difficult toachieve coatings which provide good attenuation of direct solarradiation, that is, good anti-solar properties. There has long been needin the glazing industry for coating systems which can be uniformlydeposited, especially by sputtering onto large surface areas with fastdeposition rates, low deposition power density, good film quality,including high film durability, bulk or near bulk density, and longshelf life. As used here, large area deposition refers to depositiononto transparent substrates suitable in size for architectural andautomotive glazing applications.

[0005] It is an object of the present invention to provide coatedarticles meeting some or all of these industry needs. In particular, itis an object of at least certain preferred embodiments of the inventionto provide heat-treatable coated glass articles comprising asubstantially transparent glass substrate with a substantiallytransparent coating on the surface of the substrate, which coating hasgood transmittance of visible light as well as good anti-solarperformance characteristics. In accordance with certain preferredembodiments, it is a further object to provide glazing unitsincorporating such coated glass. It is an object of at least certainpreferred embodiments of the invention to provide heat-treatable coatedglass articles comprising a substantially transparent glass substratewith a substantially transparent coating on the surface of thesubstrate, which coating has medium level of transmittance of visiblelight as well as extremely high anti-solar performance characteristics.Such coated articles can be used for architectural purposes andautomotive applications, e.g., windshields with heat shieldingproperties, or windshields with defrosting and anti-fogging properties.

[0006] It is a further object of the invention to provide methods ofmanufacturing the aforesaid coated articles. In accordance withpreferred embodiments, such manufacturing includes applying a coating inaccordance with the invention. Optionally, the methods disclosed herefurther include the steps of applying an electrically conductive busbar, if desired, and performing heat treatment of the coated article,e.g., bending or tempering, and also optionally conducting laminatingprocesses.

[0007] Additional objects and advantages of the present invention willbe readily understood by those skilled in the art given the benefit ofthe following disclosure of the invention and detailed description ofpreferred embodiments.

SUMMARY

[0008] In accordance with a first aspect of the invention, aheat-treatable, coated glass article of manufacture comprises asubstantially transparent substrate with a substantially transparentmulti-layer coating on a surface of the glass substrate. Thesubstantially transparent coating comprises a first anti-reflectionlayer of dielectric material overlying the surface of the substrate.Preferably, the anti-reflection layer is directly on the surface of thesubstrate. As used here and in the appended claims, any particular layerof the substantially transparent, multi-layer coating is said to be“directly” on or to “directly” overlie the substrate or another layer ofthe coating if no other layer of the coating is positioned between them.In this regard, any particular layer of the coating may be said to liedirectly on another layer of the coating notwithstanding that there maybe a slight transition zone between the two layers involving migrationof the material of one layer into the other and/or interlayer reactionproducts different from the primary composition of the layers. A firstbuffer layer, most preferably a chromium buffer layer, overlies thefirst anti-reflection layer. Preferably it lies directly on theanti-reflection layer. A chromium buffer layer, as that term is usedhere, means a layer which is essentially metallic chromium, such as alayer deposited by sputtering from a chromium metal target in an inertatmosphere. It may be in part oxidized, especially in preferredembodiments wherein the chromium buffer layer scavanges oxygen from anadjacent silver or copper metal or silver-copper mixed metal IRreflective layer and/or from anti-reflection layers during a heattreatment step, as further discussed below. An infrared reflective layerof silver metal or copper metal or silver-copper mixed metal directlyoverlies the first chromium buffer layer. A second chromium buffer layerdirectly overlies the infrared reflective layer. Finally, a secondanti-reflection layer of dielectric material overlies the second bufferlayer. Preferably, it directly overlies the second buffer layer.Preferably, the first and second anti-reflection layers of dielectricmaterial are SnO₂, in view of the good D.C. magnetron sputter depositionproperties of SnO₂ and its compatibility with other preferred materialsof the film stack coating disclosed here. Other suitable anti-reflectivematerials for use in the coating include other oxide and nitradematerials, such as, for example, WO₃, TiO₂, ZnO, BiOx and Si₃N₄.Additional suitable anti-reflection layer materials will be apparent tothose skilled in the art given the benefit of this disclosure.Similarly, the use of copper, copper-silver, or most preferably silverin the IR reflective layer, especially with the chromium buffer layerssandwiching it, provides highly durable coatings which areheat-treatable and, in fact, even yield improved spectral propertiesupon undergoing heat-treatment. That is, especially in preferredembodiments, heat treatment of the system with or without the IRreflective layers shows several significant effects. First, opticaltransmittance of the coated article improves upon heat treatment. Thereis a temperature threshold to start transparency improvement, around400° C., to start the oxidation of the buffer layers. Second, electricalresistance reduces upon heat treatment e.g., sheet resistance of 6 Ohmmay be reduced to 3 Ohm after heat treatment. This improvement in sheetresistance is believed due to the diminishing of interface scattering atthe abrupt Ag—Cr. The degree of interface by forming an extendedinterface of Ag—CrOx upon heat treatment. Crystalinity degree of the Agfilm may also improve upon heat treatment, producing increasedconductivity. This effect is achieved at least in preferred embodimentswithout noticeable degradation in the IR properties of the system. Thisexcellent electrical conductance of the system allows the electricalheating of the coated glass in certain preferred embodiments byconducting an electrical current through the Ag layer. Third, opticaltransmittance of the system with anti-reflecting oxide layers improves,as does durability as compared with buffer-silver-buffer three-layersystem.

[0009] Unless the individual instance of usage clearly indicatesotherwise, reference herein to heat-treatable glass should be understoodto mean glass with a coating according to the present invention, whichhas not been heat-treated (but which can undergo heat treatmentsuccessfully in accordance with the principles disclosed here) or whichhas not been heat-treated. The term heat-treated is used to mean glasswhich has been subjected to a heat-treating process, such as tempering,annealing and/or bending, etc.

[0010] It is one advantage of the present invention that theheat-treatable, coated glass articles disclosed here exhibit certainimprovements or changes in spectral properties upon undergoingheat-treating (e.g., at temperatures of about 600° C.). Visible lighttransmittance increases and sheet resistance decreases, and bothmechanical stability and environmental stability improve withheat-treating. In a typical embodiment employing a multi-layer coatingdeposited by D.C. magnetron sputtering on clear soda-lime-silica glasshaving a glass thickness from 2.2 mm thick for an automotive windshieldapplication to 6 mm thick for common architectural applications, usingSnO₂ layers about 20 nm to 60 nm thick for the anti-reflection layers,chromium buffer layers about 1 to 4 nm thick, and a silver metal IRreflectance layer 6 nm to 17 nm thick, emissivity may improve,typically, from a value of 0.15 to 0.01, visible transmittance mayincrease or may reduce, e.g., from a value of about 85% to about 70%,and sheet resistance will improve from about 13 Ohm/sq. to only about1.5 Ohm/sq., with no haze occurring. Thus, the coated glass disclosedhere can be used as different products. Before heat treatment, coatedglass in accordance with an embodiment of the invention may havegrey-blue color and Tvis of 50% to 70%. After heat-treating, the sameglass may have Tvis of about 70% to 85% and be colorless.

[0011] In accordance with certain preferred embodiments, suchheat-treatable, coated glass is especially well-suited for use in motorvehicle windshield applications with high transmittance, low visiblelight reflectance and high energy reflectance, wherein a polyvinylbutyryl or other suitable polymer sheet is sandwiched between one coatedglass sheet as disclosed here and an uncoated sheet. Certain especiallypreferred embodiments employing a coating having the above five layercoating structure, wherein the first buffer layer is a chromium bufferlayer of 2 nm and the second buffer is a chromium buffer layer of 2.5nm, and the infrared reflective layer is a silver metal layer 10 nmthick, when the glass of the windshield (in total for both glass sheets)is about 2.2 mm thick soda-lime-silica glass, have visible lighttransmittance greater than 76%, solar energy transmittance less than50%, and solar reflectance (IR region) of at least 25%. In suchespecially preferred windshield embodiments, and in other preferredembodiments of the invention disclosed here, the infrared reflectorlayer is silver and each of the chromium buffer layers has a thicknesswhich is about 10% to 30% of the thickness of the silver layer afterheat treatment. In such especially preferred windshield embodiments, andin other preferred embodiments of the invention disclosed here, thefirst buffer layer is about 20% thinner than the second buffer layer.

[0012] In accordance with certain preferred embodiments, suchheat-treatable ,bendable, coated glass is especially well-suited for usein architectural applications, especially for round buildings orbuildings with cylindrical outside elevators. Certain especiallypreferred embodiments employing a coating having the above five layercoating structure, wherein the buffer layers are chromium buffer layersof 4 nm for first buffer and 4 nm for the second buffer the infraredreflective layer is silver metal 14 nm thick, and the glass of about 6mm thick soda-lime-silica glass, have the ratio of visible lighttransmittance/total solar energy transmittance of about 50/27. Thisassumes, for example, a 6 mm-12 mm-6 mm two pane configuration, with thecoating at the surface No. 2. Such terminology, when used herein, meansthat a first 6 mm pane in spaced 12 mm from the second 6 mm No. 1; itsinside surface is surface No. 2; etc.

[0013] In accordance with another aspect, a heat-treatable coated glassarticle is provided, having a substantially transparent coating,preferably deposited on soda-lime-silica glass by D.C. magnetronsputtering, wherein the coating comprises:

[0014] a first anti-reflection layer of dielectric material overlyingthe glass substrate

[0015] a first buffer layer overlying the first anti-reflection layer

[0016] a first infra-red reflective layer of silver metal directlyoverlying the first buffer layer

[0017] a second buffer layer directly overlying the infra-red reflectivelayer

[0018] a second anti-reflection layer of dielectric material overlyingthe second buffer layer

[0019] a third buffer layer overlying the second anti-reflection layer

[0020] a second infra-red reflective layer of silver metal directlyoverlying the third buffer layer

[0021] a fourth buffer layer directly overlying the second infra-redreflective layer

[0022] a top anti-reflection layer of dielectric material overlying thefourth buffer layer.

[0023] In accordance with certain preferred embodiments, suchheat-treatable, coated glass is especially well-suited for use in motorvehicle windshield applications, wherein a polyvinyl butyral (PVB) orother suitable polymer sheet is sandwiched between one coated glasssheet as disclosed here and an uncoated sheet. Such preferredembodiments have very low reflectance of visible light and hightransmittance of visible light, as well as low total solar energytransmittance and high solar reflectance (IR region). Certain especiallypreferred embodiments employing a coating having the above nine layerfilm stack, wherein the buffer layers are chromium buffer layers of 1 nmto 4 nm thickness, the infrared reflective layer is silver metal around50 nm to 60 nm thick, when the glass of the windshield (in total forboth glass sheets laminated with PVB) is about 5.5 mm thicksoda-lime-silica glass, have visible light transmittance greater than75%; total solar energy transmittance less than 50%; and solarreflectance (IR region) of at least 25%. In such especially preferredwindshield embodiments, and in other preferred embodiments of theinvention disclosed here, each infrared reflector layer is silver andeach of the chromium buffer layers has a thickness which is about 10% to30%, the thickness of the silver layer after heat treatment.

[0024] The chromium buffer layers are found to perform a crucial role inrendering the coated glass articles disclosed here durable andeffective. Without wishing to be bound by theory, it is currentlyunderstood that the chromium buffer layers, although deposited aschromium metal, oxidize to some degree, especially during heat-treatmentof the coated glass. The buffer layers oxidize by taking oxygen fromadjacent layers, such as SnO₂ or other oxide material of an adjacentanti-reflection layer. There is a resulting increase in volume of thechromium buffer layer and corresponding increase in buffer layer densitywithout cracking of the buffer layer. This is highly advantageous, sincethe buffer layer should be crack-free and void-free following heattreatment to prevent oxygen diffusion through the buffer layer to thesilver metal IR reflection layer. Also, the high-density of the bufferlayers reduces or eliminates the adverse affects of migration of silverinto the buffer layers. Thus, long term durability and performance areachieved in the multi-layer coated, heat-treatable glass articlesdisclosed here. In preferred motor vehicle windshield embodiments of thepresent invention, the multi-layer heat-treatable coating is provided onone of the two glass panes which sandwiched between them a PVB sheet.Preferably, the coating is provided on the inside glass pane (i.e., theone facing the exterior pane vehicle passenger compartment rather thanthe exterior pane), most preferably on the so-called surface No. 2 ofthe windshield, i.e., on the outside surface of the inside pane (i.e.,adjacent the PVB sheet). The two glass panes, one coated and oneuncoated, typically are paired and bent together. In accordance withpreferred embodiments, special powder to prevent the glass panessticking together are usually used between the matched panes during suchbending process can be eliminated. The multi-layer coating serves toprevent sticking. Moreover, the multi-layer coating in accordance withpreferred embodiments is sufficiently durable and though, that it can beplaced into contact with the second glass pane during the bendingprocess without causing unacceptable scratching or other degradation ofthe coating.

[0025] In accordance with another aspect of the invention, methods areprovided for making the coated article disclosed above. Such methodscomprise providing a substantially transparent substrate, typically withappropriate surface preparation steps being performed on the surface tobe coated. The multi-layer, anti-solar coating is then formed on thesurface of the substrate. The first anti-reflection layer of dielectricmaterial is deposited, followed by the first chromium buffer layer,followed by the silver metal infra-red reflective layer, followed by thesecond chromium buffer layer, followed by the second anti-reflectionlayer. In accordance with preferred embodiments, each of the layers ofthe substantially transparent coating is deposited by sputtering in aseries of sputter stations arranged sequentially in a single sputteringchamber through which the transparent substrate passes at constanttravel speed. Suitable partitions, such as curtains or the like,separate one sputter station from the next within the sputteringchamber, such that different deposition atmospheres can be employed atdifferent stations. A reactive atmosphere comprising nitrogen or oxygenor both can be used, for example, at a first station to deposit ananti-reflection layer, followed by a non-reactive atmosphere consistingessentially of argon or other suitable inert gas at a subsequent stationfor depositing the silver metal IR reflection layer.

[0026] In accordance with certain highly preferred embodiments of themanufacturing method disclosed here, the substantially transparentcoating is deposited by multiple passes, preferably two passes throughsuch multi-station sputtering chamber. If the multi-station sputteringchamber has a sufficient number of cathodes, e.g., at least nine cathodematerials mentioned above, this method is especially suitable, forexample, for depositing the nine layer coating disclosed above in asingle pass. Alternatively, during each of the passes through thesputtering chamber, a multi-layer coating is deposited comprising theaforesaid first anti-reflection layer, first chromium buffer layer,silver metal layer, second buffer layer and second anti-reflectionlayer. Coatings formed in accordance with such multi-pass methods of theinvention are found to have substantially improved coating properties,including especially colour spectral uniformity.

[0027] It will be apparent to those skilled in the art in view of thepresent disclosure, that the present invention is a significanttechnological advance. Preferred embodiments of the substantiallytransparent coatings disclosed here have excellent spectral performancecharacteristics, including excellent transmittance of visible light andadvantageously high anti-solar properties, that is, high attenuationlevels of direct solar radiation. Employing the above disclosed silvermetal infra-red reflective layer, sandwiched between chromium bufferlayers, together with the anti-reflection layers results in novelmulti-layer coatings which are highly suitable for large area depositionby planar DC magnetron sputtering. Fast deposition rates can beobtained, even employing advantageously low deposition power densities.The resulting coating has high durability, bulk or near bulk density andlong shelf life.

[0028] Additional features and advantages of the various embodiments ofthe present invention will be further understood in view of thefollowing detailed description of certain preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Various preferred embodiments of the coated article ofmanufacture and method of manufacture disclosed above are discussedbelow with reference to the appended drawing in which:

[0030]FIG. 1 is a schematic cross-sectional view of a coated article ofmanufacture according to a first preferred embodiment;

[0031]FIG. 2 is a schematic cross-sectional view of a second preferredembodiment;

[0032]FIG. 3 is a schematic illustration of a motor vehicle windshield(partially broken away) in accordance with a preferred embodiment,having the coating of FIG. 2 on surface No. 2 of the glazing panes; and

[0033] FIGS. 4-7 are graphical representations of the spectralproperties of various preferred embodiments described in Examples 1-3,respectively;

[0034] It should be understood that the schematic illustrations in FIGS.1-3 are not necessarily to scale. In particular, the thickness of thevarious individual layers forming the substantially transparentmulti-function coating are increased relative the thickness of thesubstrate for the purpose of clarity and ease of illustration.

DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS

[0035] The coatings disclosed here are thermostable in that, whensubjected to thermal stress, they are resistant, against degradation,most notably in their capacity to block or transmit light. In addition,the term “thermostable” refers to a coating or coated article ofmanufacture which substantially retains its characteristic mechanicalproperties, such as body integrity, surface continuity, tensile strengthand adhesiveness (e.g., between coating and substrate). The term“thermal stress” is herein taken to mean the stresses encountered uponexposure to high temperatures used for heat treatment, e.g., fortempering or bending the glazing substrate. Typically, such temperaturesare in the range of 590° C. to 650° C. The solar coatings of theinvention are thermostable at the tempering temperature of the glazingsubstrate and/or at its bending temperature.

[0036] It will be apparent to those skilled in the art, given the abovedisclosure and the following detailed description, that the coatedarticles disclosed here, comprising a substantially transparent glasssubstrate carrying a substantially transparent coating have numerouscommercially significant applications. For ease of discussion, thefollowing detailed description of certain preferred embodiments willfocus primarily on articles suitable for automotive or architecturalglazing applications. It will be within the ability of those skilled inthe art, given the above disclosure and this detailed description, toemploy the invention in alternative applications.

[0037] Referring now to FIG. 1, a coated article 10 is seen to comprisea substantially transparent substrate 12 having a main surface 14carrying substantially transparent, multi-layer coating 16. In preferredembodiments, the substantially transparent substrate is a flat orcurvo-planer pane of glass or glass ceramic. It is highly preferred thatthe substantially transparent substrate be a panel of glass selectedfrom the group consisting of soda-lime-silica glass, borosilicate glass,aluminosilicate glass, vycor, fused silica and vitreous silica. It isparticularly preferred that the glass be soda-lime-silica glass. Coating16 provides thermal insulation or anti-solar performance characteristicsfor the coated article. Coating 16 includes a first anti-reflectionlayer 18 directly on the surface 14. Numerous suitable materials foranti-reflection layer 18 are disclosed above and will be apparent tothose skilled in the art given the benefit of this disclosure. Mostpreferably anti-reflection layer 18 is formed of S_(n)O₂. It should beunderstood that all references here and in the appended claims to anoxide, unless otherwise clear the context of any particular instance ofits use, are intended to include variations in the degree of oxidation.Chromium buffer layer 19 lies directly on anti-reflection layer 18.Silver metal layer 20 lies directly on buffer layer 19. Second bufferlayer 22 directly overlies silver metal layer 20. The overlyinganti-reflection film 24 is exposed to the atmosphere. It will be withinthe ability of those skilled in the art, given the benefit of thisdisclosure, to determine suitable thickness for the individual layers ofcoating 16, given the benefit of the disclosure, including suitablethickness for silver metal layer 20 adapted to the intended applicationof the coated article. Silver metal layers of greater thickness willprovide enhanced infra-red reflectivity, while thinner silver metallayers will provide increased transmittance of light in the visiblewavelength range. In accordance with certain preferred embodiments, thesilver metal layer has a thickness between 6 nm and 18 mm, morepreferably between 8 nm and 12 nm for automotive applications andbetween 8 nm and 16 nm for architectural applications.

[0038] It will be within the ability of those skilled in the art, giventhe benefit of this disclosure, to employ additional coatings oradditional coating layers with the multi-layer, heat-treatable, thermalinsulation coatings disclosed here. For example, transparent oxide ornitrite over-layers may be used at the surface of the coating exposed tothe atmosphere. Also, colour control layer(s) can be used, preferably atthe interface of the coating with the glass substrate or on a differentsurface of the glass substrate. One or more other additional coatingsmay be used, e.g., an all-dielectric anti-reflecting coating system on adifferent surface of the glass substrate, preferably on the number 4surface of a double pane (interior side). Such AR coating improves thevisible transmittance of the overall coated article. Also, adhesionenhancing layer(s) can be used, e.g., at the interface of the coatingwith the glass substrate or on a different surface of the glasssubstrate.

[0039] The adhesion increasing layer or colour forming layer preferablyhas a thickness less than 50 Å and is formed preferably of silicon ortungsten metal. It will be within the ability of those skilled in theart, given the benefit of this disclosure, to select a suitable materialand thickness for the colour control layer to achieve both enhanceduniformity and desired hue or colour of the coated article. Referencehere to uniformity of colour refers to reduction in blotchiness or thelike which may otherwise appear in a coated article

[0040] An alternative preferred embodiment of the coated articlesdisclosed here is illustrated in FIG. 2, having a substantiallytransparent soda-lime-silica glass substrate 32. A substantiallytransparent, heat-treatable coating 36 is carried on surface 34 ofsubstrate 32. In coating 36, first anti-reflection layer 38 directlyover the surface 34 of substrate 32.

[0041] The anti-reflection layer 38 in coating 36 of coated article 30is comparable to anti-reflection layer 18 in the embodiment of FIG. 1.Directly overlying anti-reflection layer 38 is a first buffer layer 40,preferably a chromium buffer layer, for the reasons discussed above.Silver metal layer 42 in the embodiment of FIG. 2 corresponds generallyto silver metal layer 20 in the embodiment of FIG. 1. Similarly, secondbuffer layer 44 corresponds generally to buffer layer 22 in theembodiment of FIG. 1. It will be within the ability of those skilled inthe art to select a suitable thickness for buffer layer 40, inconjunction with selection of the thickness of buffer layer 44, toprovide good protection for the silver metal layer 42 and the otherlayers of coating 36 within the constraints of meeting spectralperformance requirements in the finished article. Oxide layer 46directly overlies record buffer layer 44, and may be deposited in twoparts. Specifically, if a double pass sputtering deposition is carriedout as disclosed above, a first portion of oxide layer 46 may bedeposited at the last deposition station during the first pass of theglass substrate through the sputtering chamber. The second portion wouldthen be deposited at the first deposition station during the final pass.Third buffer layer 48 directly overlies oxide layer 46. Second IRreflection layer 50 directly overlies third buffer layer 48. Fourthbuffer layer 52 directly overlies silver metal layer 50. Outeranti-reflective layer 54 directly overlies fourth buffer layer 52, andis exposed to the atmosphere or to the space between pane 32 and asecond, coated or uncoated pane used with pane 32 to form adouble-glazed unit. Such space between two panes can be a vacuum orfilled with inert gas. The coated surface also can be positioned to lieagainst a PVB laminating sheet in a windshield construction or the like.Anti-reflection film 54 in the embodiment of FIG. 2 correspondsgenerally to tin oxide or other oxide anti-reflection layer 24 in theembodiment of FIG. 1. The thickness of the outer anti-reflection layer,that is, anti-reflection layer 24 in FIG. 1 and 44 in FIG. 2, isselected to provide, in conjunction with the other layers of thecoating, suitably low reflectance of visible light, with reflectancecolor preferably being neutral or grey-blue in the unheat-treatedcondition.

[0042] In accordance with certain preferred embodiments, the coatedarticle 30 is subjected to a tempering step subsequent to deposition ofthe coating 36. Coating 36 survives exposure to the high temperaturesrequired for tempering a glass substrate, such as a soda-lime-silicaglass substrate intended for architectural or automotive applications.

[0043]FIG. 3 illustrates a motor vehicle windshield partially brokenaway, in accordance with a preferred embodiment. A first pane 62 islaminated to a record sheet 64 by PVC sheet 66 between them. The insidepane 62, i.e., the one toward the motor vehicle passenger compartment,was bent in tandem with outer pane 64 and then separated for laminating.A heat-treatable, multi-layer coating 70, in accordance with the presentdisclosure is on surface No. 2 of the windshield, i.e., inside surface68 of outside pane 64. Preferably coating 70 is in accordance with thecoating shown in FIG. 1 or FIG. 2. Above figure showing two panes ofglass window, withe the temperable multi functioning coating on the No.2 surface is necessary here.

[0044] The heating temperature/time profile of the bending furnace orlehr used for bending a heat-treatable coated glazing of the presentinvention is important. Suitable lehrs include, for example, a Tamglassbending furnace for simultaneous shaping of the two panes of anautomobile windshield by gravity sag forming. The top pane preferably iscoating free and the inside of the lower pane comprises the coating.Such bending furnace has five thermal zones. A first heating zone isfrom room temperature to 350° C. A second heating zone is from 350° C.to 620° C. A third heating zone is the bending zone and the last twozones are the cooling regions where glass cool downs slowly at first andthen faster. The total time of the bending process is typically about 30minutes: 15 min. for heating & bending and 15 min. for cooling. The bestresults of bending in the third zone occur for typical automotivesoda-lime-silica glass, at about 615° C. over 45 to 60 seconds. It willbe within the ability of those scheduled in the art to determinealternative suitable temperature/time profiles given the benefit of thepresent disclosure.

[0045] Preferred embodiments of the coated articles disclosed here canbe prepared in accordance with various suitable techniques employingcommercially available equipment and materials. Preferably, thesubstantially transparent dual-function coating is formed on the surfaceof the substantially transparent substrate by cathodic sputtering. Inaccordance with certain preferred embodiments, a coated article ismanufactured by depositing each of the layers of the coating insequence. Preferably, each of the layers is deposited in turn as thesubstrate travels continuously through a multi-station sputteringchamber. Thus, in manufacturing the embodiment of FIG. 1, for example,as the substrate passes through a first sputtering station within suchmulti-station chamber, the first anti-reflection layer of dielectricmaterial is deposited by DC magnetron sputtering onto the surface of thesubstrate. Depending on the substrate travel speed, depositionparameters, and the thickness of the anti-reflection layer, one, two ormore sputtering stations can be used to deposit the same coatingmaterial. In this way, one can achieve shorter deposition cycle time.After having deposited the first anti-reflection layer onto the glasssurface, the buffer layer and infrared reflective layer are thendeposited by sputtering as the substrate passes through a subsequentstation of the multi-station chamber. The second buffer layer isdeposited at a subsequent station within the chamber, and then thesecond anti-reflection layer is deposited on a subsequent station.Preferably, the substrate moves continuously through the chamber, suchthat the individual layers are deposited onto the substrate as it istraveling. The individual stations are sufficiently isolated by curtainsor other suitable partition means, such that the reactive atmosphereemployed at a first sputtering station does not contaminate thenon-reactive atmosphere employed at an adjacent station. In this regard,where less than all stations of a multi-station deposition chamber areto be employed, for example, where an eight-station chamber is to beused to deposit a four-layer coating, a station can be left unusedbetween one employing a reactive atmosphere and another employing anon-reactive atmosphere to achieve better isolation. Suitablemulti-station sputter deposition chambers are commercially available,including pilot plant size coaters, for example, Model Z600 from BalzersProcess System GmbH, D-63755, Alzenau, Germany, and full commercialscale coaters, for example, Interpane 1993 model Coater available fromInterpane Glass Industrie AG, Sohnr Eystasse 2137697 Lauenförde,Germany. Table A gives the typical process parameters for Model Z600pilot plant coater and for an Interpane 1993 Model production coater.Parameters Z600 Interpane Maximum Substrate 40 × 50 600 × 300Dimensions, cm Background Pressure, 5 5 mbar (10⁻⁵) Power Density(Watt/cm²) 0.2-5 0.2-5 Working Pressure, 1.5-4 2-7 mbar (10⁻³) Argon,sccm sputter sputter Oxygen, sccm reactive reactive Nitrogen, sccmreactive reactive

[0046] Advantageously, such preferred multi-station sputtering chambersemploy sputter targets which are wider than the glass substrates beingcoated and are mounted in a direction extending perpendicular to thetravel direction of the substrate. It will be within the ability ofthose skilled in the art to select suitable deposition conditions andparameters for magnetron DC sputtering of the various layers disclosedabove for the transparent coated articles of the present invention. Thefollowing deposition parameters are suitable for a typical depositionprocess to produce a heat-treatable, multi-layer coating in accordancewith the embodiment of FIG. 1 coating on a soda-lime-silica glasssubstrate 40 cm wide by 50 cm long traveling at a rate of 2 meters perminute through the sputtering chamber.

[0047] 1. The sputtering chamber is initially evacuated to about 5×10⁻⁵millibar and then raised to an operating pressure of approximately3×10⁻³ millibar by the injection of operating gases at the varioussputtering stations.

[0048] 2. Tin oxide anti-reflection layers are deposited by sputteringfrom a pure tin target in an operating atmosphere of 3.2×10⁻³ millibarwith an Argon/Oxygen flow rate ratio of 45/82, at a power level of about4 to 5.5 Watts/cm². The throw distance from the tin target to thesubstrate is typically about 5 to 15 cm.

[0049] 3. The silver infra-red reflective layer is deposited from a puresilver target in a non-reactive atmosphere, for example, a substantiallypure argon atmosphere, in an operating atmosphere of 2.0×10⁻³ millibarat a power level of about 0.4 to 2.6 Watts/cm². The throw distance fromthe silver target to the substrate is typically about 5 to 15 cm.

[0050] 4. The chromium buffer layers are deposited from a chromiumtarget in a non-reactive atmosphere, for example, a substantially pureargon atmosphere, in an operating atmosphere of 11×10⁻⁴ millibar at apower level of about 0.4 to 1.0 Watts/cm². The throw distance from thesilicon target to the substrate is typically about 5 to 15 cm.

[0051] In accordance with certain preferred embodiments, a substantiallytransparent, heat treatable coating in accordance with the structure ofthe embodiment of FIG. 2 described above is formed by passing thesubstrate through the multi-station sputtering chamber a first time,followed by passing it through the sputtering chamber a second time.Preferably the deposition characteristics and process parameters aremaintained the same before the two passes, such that substantiallyidentical sets of layers are deposited during each pass. Optionally, aslightly thicker final oxide layer is deposited for enhanced performancecharacteristics. In general, it would be understood that the thicknessof the deposited layers will be determined largely by the depositionpower level, working gas conditions, and the exposure time. The exposuretime is determined primarily by the speed at which the substrate istraveling through the sputtering chamber, although additional thicknesscan be achieved by employing multiple targets for a deposited layer.Throw distance is also a significant factor in determining layerthickness. In preferred embodiments employing sputtering targets widerthan the substrate, advantageously small throw distances can be usedwithout sacrificing uniformity of deposition thickness.

[0052] It has been found that, generally, multi-pane glazing systemsemploying the heat-treatable coating of the present invention providebest results when the coating is placed at the second surface asillustrated in FIG. 3.

[0053] The present invention is further disclosed by the followingexamples, which are intended for purposes of illustration and notlimitation.

EXAMPLES

[0054] The following examples illustrate coated articles according tothe invention, and their manufacture. In each of the following examples,a soda-lime-silica glass panel 30 cm wide by 30 cm long by 6mm thick ispassed through a multi-station sputtering chamber, Model Z600 availablefrom Balzers Process System. At the same time, for visual inspection,measurement and characterizations, test pieces also were coated in thesystem. That is, same, a 5 cm wide by 5 cm long by 2.2 mm thick glasswas used for windshield applications and the same size test pieces of 6mm thick samples for architectural applications. The glass paneltraveled in each case through the sputtering chamber at a travel speedof 2 meters per minute. Immediately prior to entering the sputteringchamber, the glass panel surface to be coated was washed withdemineralized water (max 5 microsiemens) and substantially dried bypressurized air. For each of the examples, the sputtering conditions areprovided for each layer of the dual-function coating. In those of theexamples involving a double-layer structure, as disclosed above, thedeposition conditions and parameters were identical for the first andsecond passes unless otherwise stated.

[0055] The spectral properties were measured for the resultant coatedarticle of each example. Perkin Elmer Model Lambda 900 UV Vis NIRspectrophotometer was used to measure the optical performance of eachsample, e.g., transmittance, T %, reflectance from film side, R %, andreflectance from glass side, R′ %, with all spectra being measured overthe 350 nm-2100 nm spectral region. Reference herein to spectralproperties in the IR range mean 750 nm to 2100 nm. The weighted spectralaverages of the visible region, T_(vis), R_(vis), R′_(vis) and otherperformance and color information shown in Tables 1-6 were determined bythe “Window 4.0”, and Uwinter and Usummer were calculated using the“Window 4.1” calculation program both publicly available from the USADepartment of Energy. These “U” values are a measure of overallconductance of the thermal energy in terms of Watt/m² K, calculatedusing the following table: Outside Temp Inside Temp Wind Speed WindDirect Solar T_(sky) Name (° C.) (° C.) (m/s) Direction (W/m²) (° C.)E_(sky) Uwinter Uvalue −17.8 21.1 6.7 0 Windward 0.0 −17.8 1.00 Solar−17.8 21.1 6.7 0 Windward 0.0 −17.8 1.00 Usummer Uvalue 31.7 23.9 3.4 0Windward 783.0 31.7 1.00 Solar 31.7 23.9 3.4 0 Windward 783.0 31.7 1.00

[0056] In addition, the R_(s) surface resistance was measured by aSignatron four probe, and emissivity, e was measured by an IRspectrometer and calculated from the following equation:

e=1−(1/((1+0.0053)×R _(s)))²

[0057] Ref.: K. L. Chopra, S. Major, D. K. Pandya. It was found thatmeasured and calculated values fit well with each other for the filmshaving surface resistance R_(s) less than 10 Omhs. The shadingcoefficient, sc, was calculated as the performance ratio,T_(vis)/T_(solar), was used to determine the quality of the coatings.The theoretical limit of the T_(vis)/T_(total) solar ratio is 2.15.

Example 1

[0058] This example shows the properties of a bendable and otherwiseheat treatable coated glass suitable for motor vehicle windshieldapplications. In Table 1 below, the coated glass of this example isidentified by reference No. 1345. The same glass following heattreatment as described below is identified in Table 1 as Sample No.t1345. The same sample following such heat treatment and then laminationto an uncoated but otherwise substantially identical glass pane by meansof a PVB polymer layer sandwiched between the two glass panes isidentified by reference number LI 345. The sample of this example is asingle silver/single pass sample. That is, the glass is passed throughthe DC magnetron sputtering chamber only once (hence, being referred toas a single pass coating) wherein it is coated, in order, with ananti-reflection layer, chromium buffer layer, silver layer, secondchromium buffer layer and finally second anti-reflection layer. Thus,the coated glass sample of this example has only a single layer ofsilver in the film stack which makes up the coating deposited on theglass in the sputtering chamber.

[0059] The glass panel was prepared and passed through the multi-stationsputtering chamber as described above. In this example, theheat-treatable multi-layer coating was SnO₂/Cr/Ag/Cr/SnO₂ where thefirst SnO₂ layer (directly on the glass substrate surface) and thetopmost SnO₂ layer have the same thickness, but the first Cr layer isthinner than the second Cr film. The total thickness of the coating wasaround 920 Å.

[0060] At station 1 within the multi-station sputtering chamber, a 39 nmthick layer of SnO₂ was deposited by sputtering from a tin target at 5.1Watts/cm² in an atmosphere of Argon and Oxygen gasses with the flowratio of 45 to 82 sccm (i.e., with Argon and Oxygen flow rates of 45sccm and 82 sccm, respectively) at a vacuum level of 3.2×10 ⁻³ mbar.

[0061] At station 2, within the multi-station sputtering chamber, a 2 nmthick layer of Cr was deposited by sputtering from a chromium target at0.4 Watts/cm² in an atmosphere of Argon gas with a flow rate of 20 sccmat a vacuum level of 11×10⁻⁴ mbar.

[0062] At station 3, within the multi-station sputtering chamber, a 95nm thick layer of Ag was deposited by sputtering from a Silver (Ag)target at 1.3 Watts/cm² in an atmosphere of Argon gas with a flow rateof 50 sccm at a vacuum level of 2.0×10⁻³ mbar.

[0063] At station 4, within the multi-station sputtering chamber, a 2.5nm thick layer of Cr was deposited by sputtering from a chromium targetat 0.4 Watts/cm² in an atmosphere of Argon gas with the flow rate of 30sccm at a vacuum level of 11×10⁻⁴ mbar.

[0064] At station 5, within the multi-station sputtering chamber, a 39nm thick layer of SnO₂ was deposited by sputtering from a tin target at5.1 Watts/cm² in an atmosphere of Argon and Oxygen gasses with a flowrate of 45 to 82 sccm at a vacuum level of 3.2×10⁻³ mbar.

[0065] The resultant coated glass panel, Sample No. 1345, had good coloruniformity. Its spectral properties are shown in Table 1 below, andspectral transmittance and reflection properties of the coated panel ofthis Example 1 are shown in the graphs of FIG. 4, wherein the horizontalaxis shows wavelength and the vertical axis shows level oftransmittance. Specifically, FIG. 4a shows intensity as a function ofwavelength for Sample No. 1345, that is, the coating as deposited. FIG.4b shows corresponding spectral properties for Sample No. t1345, thatis, the coating after heat treatment at 635° C. for 1 minute. FIG. 4cshows the spectral properties for Sample No. LI 345, that is, thelaminated glazing system incorporating the glazing pane carrying theheat-treated coating and laminated by means of a PVB lamination layer toa second, uncoated glazing pane. In all cases, the spectral propertiesinclude transmittance (T %), reflection measured from the coated side (R%), and reflection measured from the uncoated side (R′ %). As notedabove, coated articles of these examples were characterized byspectrophotometric measurements (Perkin Elmer Lambda 900 UV/VIS/NIRSpectrometer), resistance measurements (signatone four probes Model SYS301 instrument combined with Keithly Model 224 current source and Model2000 multimeter), and thickness measurements (Tencor Alpha Step Model500). Film thicknesses were measured by a Tencor Model Alpha step 500thickness measuring apparatus. Mechanical properties of the samples weredetermined by a Taber Abraser machine. Environmental stability of thesamples were evaluated by using a weathering cabin controlling ambienttemperature and humidity. Spectrophotometric measurements were takenover 300 nm to 2100 nm spectral region, including transmittance T %,reflection R % measured from the coated side, and reflection R′ %measured from the glass (uncoated) side. As can be seen from Table 1 andthe graphs of FIG. 4, the coated panel prepared in accordance with thisExample 1 has excellent transmittance of visible light together withgood anti-solar properties. In addition, it has excellent environmentalproperties and long shelf life, specifically, passing a test of at leasttwo weeks in the humidity chamber at 60° C. and 95% relative humiditywith substantially no degradation observed throughout the sample surfaceof 40 cm by 50 cm, including the edges of the laminated product SampleNo. 1345. Furthermore, the coating process can be seen from thedescription here to be fast and economical, so as to be commerciallysuitable for producing automotive and architectural glazing products. Inthat regard, the sputter deposition process required only approximately2.5 minutes.

Example 2

[0066] This example illustrates a double pass/double silver layercoating system. That is, in this example, the soda-lime silica glasspane is passed through the DC magnetron sputtering chamber substantiallyas in Example 1 above, but is then passed through the DC magnetronsputtering chamber a second time to produce a double-layer coating. Theresultant coating system deposited onto the glass surface has two IRreflective layers, that is, two layers of silver in the film stack whichforms the coating. It will be appreciated from the foregoing disclosureand discussion of the invention, that single pass, single silver layersystems are advantageous in that they are simpler to produce, and aresuitable for both automotive and architectural applications. Doublepass, double silver layer coating systems, however, in accordance withthe invention, also provide excellent spectral properties, environmentaldurability, etc. In accordance with this Example 2, the glass panel wasprepared and passed through the multi-station sputtering chamber asdescribed above in Example 1, except coating was doubled, that is, acoating system of SnO₂/Cr/A_(g)/Cr/SnO₂/Cr/Ag/Cr/SnO₂ system wasdeposited with the respective thicknesses (measured in nanometers) of40/2/7/2/80/2/7/2/40. The total thickness of the resultant coating wasaround 182 nm. As mentioned above, in this example the coating wasproduced by passing the glass panel twice through the coater. The samedeposition parameters were maintained during the second pass. The coatedsample of this Example 2 was subjected to heat treatment as inExample 1. The resulting heat treated sample is identified in table 1below by reference No. t1288. The corresponding sample after beinglaminated to an uncoated but otherwise substantially identical pane bymeans of a PVB laminating layer is identified in Table 1 below byReference No. L1288. The spectral properties of Sample No. t1288 andSample No. L1288 are shown in Table 1 below. Spectral transmittance andreflectance properties of the coated panel of Example 2 are shown in thegraphs of FIG. 5a and 5 b. Specifically, FIG. 5a shows the spectralproperties T, R and R′ as intensity (%) as a function of wavelength forSample No. t1288. FIG. 5b shows the corresponding spectral propertiesfor the laminated Sample No. L1288. Performance values for Sample No.tl288 and Sample No. L1288 also are given in Table 1, below. The samplesof this Example 2 were found to have excellent environmental propertiesand a long shelf life comparable to those of Example 1. Morespecifically, as can be seen from Table 2 and the graph of FIG. 5, thecoated panel prepared in accordance with this Example 2 has excellenttransmittance of visible light together with good anti-solar properties.In addition, it has excellent mechanical properties, including longshelf life. Furthermore, the coating process can be seen from thedescription here to be fast and economical, so as to be commerciallysuitable for producing automotive and architectural glazing products.

Example 3

[0067] Addition examples of the present invention were prepared to showarchitectural applications. Specifically, sheets or panes ofsoda-lime-silica glass having the same composition as in Examples 1 and2, being 6 mm thick, were used to prepare four architectural glassglazing products. In each case, a first 6 mm pane coated as describedbelow was spaced 12 mm from a second, uncoated 6 mm thick pane. Thecoating was carried on surface No. 2 of the resultant double panearchitectural glazing product. In all four samples, the coating systemwas deposited under the same conditions recited above in Example 1except as follows. In the first sample, Sample No. t 1372 IG, thechromium and silver layers were thicker than in Example 1. Specifically,the silver layer was 14 nm thick and the two chromium layers, whichsandwich the silver layer between them, were each 4 nm thick. The tinoxide layers each was 22 nm thick. The spectral properties of theresulting Sample No. 1372 (tested as a single pane corresponding to thetest of Sample 1345 shown in FIG. 4a) carrying the coating systemSnO₂/Cr/Ag/Cr/SnO₂ are shown in FIG. 6a. Specifically, spectral valuesT, R and R′ are shown in FIG. 6a as a function of wavelength. In FIG. 6bthe corresponding spectral properties for the same sample after heattreatment are shown. The heat treatment was the same as that forExample 1. Additional performance characteristics of the heat treatedSample t1372 are shown in Table 1, below.

[0068] A series of additional samples in accordance with this Example 3were prepared, having the same chromium and silver film thicknesses asfor the first Sample No. 1372, above. Specifically, each of theseadditional samples was prepared in accordance with the method of Example1, having 4 nm thick (before heat treatment) chromium layers sandwichingbetween them a 14 nm thick silver layer. The thickness of the tin oxidelayers of these additional samples was varied. More specifically, thesamples were prepared, each carrying a coating system ofSnO₂/Cr/Ag/Cr/SnO₂ on 6 mm thick glass, wherein each of the two tinoxide layers for the sample had the thickness given below. Sample No.Thickness of SnO₂ Layers t1372 22 nm t1376 35 nm t1378 55 nm t1377 65 nm

[0069] In each case, the thickness recited above is for each of the tinoxide layers, rather than for the two tin oxide layers combined. FIG. 7shows the transmission spectra for these four samples. As seen there, asthe oxide layer thicknesses increase, the transmission maxima or colorshifts from blue toward yellow. The same color shifts are observed forreflectance. Additional performance properties for these samples areprovided in Table 1, below. It should be noted that the transmissionspectra shown in FIG. 7 are for each of the samples following heattreatment as described for the sample of claim 1, at 650° C. As notedabove, the performance characteristics provided in Table 1 below are foreach of the samples used in a “6+12+6” double glazing product, that is,a double glazing wherein a first 6 mm pane carrying the respectivecoating for that sample is paired with a second 6 mm, uncoated pane witha distance of 12 mm between the two panes. Excellent mechanicalproperties, including long shelf life are obtained for the heat treatedsamples and for the double pane glazing products made using the coatedsamples of this example. TABLE 1 PERFORMANCE TABLE FOR MULTI-FUNCTIONALGLAZING SYSTEM Optical Properties Sol. Energy Visible Region RegionRelat. Reflection Reflection Therm. Prop. Shading Solar Heat ColorCoordinates System Trans. OUT IN Trans. Out In Winter Summer Coef FactorGain Transmittance Reflectance (Out) Descr. Tvis R1 R4 Tsol R1 R4 U winU sum SCc SHGCc RHG TL a* b* RL a* b* AUTOMOTIVE GLAZING 1345 0.74 0.060.05 0.47 0.26 0.32 6.20 5.99 0.63 0.54 445 88.8 −3.20 0.38 29.3 7.34−9.10 1345 0.84 0.06 0.05 0.54 0.27 0.31 6.36 6.05 0.69 0.59 483 93.2−2.20 2.64 29.6 5.23 −9.30 1345 0.76 0.12 0.12 0.48 0.29 0.26 6.24 5.980.63 0.54 444 90.1 −3.70 1.96 40.5 5.94 5.89 1288 0.76 0.07 0.07 0.500.27 0.30 6.36 6.10 0.65 0.56 458 89.8 −0.30 1.77 31.7 3.49 1.22 12880.75 0.07 0.07 0.44 0.29 0.26 6.20 6.00 0.60 0.51 423 89.1 −2.00 3.7332.7 0.75 −1.10 ARCHITECTURAL GLAZING (6 + 0.50 0.33 0.34 0.23 0.45 0.461.63 1.65 0.31 0.27 211 76.6 −12.00 −1.60 63.2 10.30 16.10 12 + 6) t1372IG (6 + 0.37 0.47 0.48 0.20 0.49 0.50 1.63 1.65 0.28 0.24 188 68.6 −9.80−16.00 73.1 2.64 31.70 12 + 6) t1372 IG (6 + 0.44 0.33 0.37 0.22 0.410.44 1.63 1.65 0.31 0.26 206 71.5 −4.60 14.90 64.1 1.35 −7.80 12 + 6)t1372 IG (6 + 0.49 0.33 0.32 0.23 0.44 0.45 1.63 1.65 0.33 0.29 236 75.3−8.50 11.00 63.8 3.59 −1.00 22 + 6) t1372 IG

[0070] It will be apparent from the foregoing disclosure thatalternative embodiments are possible within the scope of the invention,including, for example, modifications to the preferred embodimentsdescribed above. It will be recognized by those skilled in the art,given the benefit of the present invention, that coated articles ofmanufacture in accordance with the present invention can be preparedwhich are more or less colorless, depending on the thicknesses of thevarious films employed to form the coating. In particular, increasingthe thickness of one or more of the anti-reflection oxide layers and/ordecreasing the thickness of the silver infra-red reflective layer can beemployed to provide a more colorless sample. This is consistent with thediscussion in Example 7, above. Correspondingly, a more color-formingarticle can be prepared by decreasing the thickness of theanti-reflection layers and increasing the silver layer thickness.Additional alternative embodiments of the present invention, includingthose employing SnO₂ and the like can be employed in accordance with theprinciples disclosed here to provide color-forming or colorless coatedarticles within the scope of the present invention.

What is claimed is:
 1. A heat-treatable coated glass article comprisinga substantially transparent glass substrate with a substantiallytransparent coating on a surface of the glass substrate, thesubstantially transparent coating comprising: a first anti-reflectionlayer of dielectric material overlying the glass substrate, a firstchromium buffer layer overlying the first anti-reflection layer, aninfra-red reflective layer of metal selected from silver metal, coppermetal and a mixture of both, directly overlying the first buffer layer,a second chromium buffer layer directly overlying the infra-redreflective layer, and a second anti-reflection layer of dielectricmaterial overlying the second buffer layer.
 2. The coated article ofmanufacture according to claim 1 wherein the infra-red reflective layeris silver metal and the first and second anti-reflection layers each isSnO₂.
 3. The heat-treatable coated glass article according to claim 2wherein the thickness of each chromium buffer layer is 10% to 30% of thethickness of the infra-red reflective layer of silver metal.
 4. Theheat-treatable coated glass article according to claim 2 wherein thethickness of each chromium buffer layer is 1 nm to 5 nm and thethickness of the infra-red reflective layer of silver metal is 6 nm to13 nm.
 5. The heat-treatable coated glass article according to claim 4wherein the first and second anti-reflection layers of SnO₂ each has asubstantially uniform thickness from 20 nm to 50 nm.
 6. Theheat-treatable coated glass article according to claim 1 wherein saidglass is not heat-treated and, when the glass has a thickness of about2.2 mm to 6 mm, has the following characteristics: grey-blue color andsubstantially free of haze; visible transmittance of 40% to 70%; andsheet resistance of not more than 7 ohms/sq.
 7. The heat-treatablecoated glass article according to claim 1 wherein said glass isheat-treated clear glass and, when the glass has a thickness of about2.5 mm to 6 mm, has the following characteristics after heat-treatment:substantially free of haze; visible transmittance of 50% to 80%; andsheet resistance of not more than 5 ohms/sq.
 8. The heat-treatablecoated glass article according to claim 1 wherein the firstanti-reflection layer lies directly on the surface of the glass.
 9. Theheat-treatable coated glass article according to claim 8 wherein thefirst chromium buffer layer lies directly on the first anti-reflectionlayer.
 10. The heat-treatable coated glass article according to claim 9wherein the infra-red reflective layer directly overlies the firstchromium buffer layer.
 11. The heat-treatable coated glass articleaccording to claim 10 wherein the second chromium buffer layer directlyoverlies the infra-red reflective layer.
 12. The heat-treatable coatedglass article according to claim 11 wherein the second anti-reflectionlayer directly overlies the second buffer layer.
 13. The heat-treatablecoated glass article according to claim 1 wherein the substantiallytransparent glass substrate is soda-lime-silica glass.
 14. A motorvehicle windshield comprising a polymer sheet sandwiched between a firstheat-treated glass substrate bent to a curved shape, a secondheat-treated glass substrate bent to a matching curved shape, and asubstantially transparent coating on a surface of at least one of theheat-treated glass substrates, the substantially transparent coatingcomprising: a first anti-reflection layer of SnO₂ overlying the glasssubstrate and having a thickness of about 39 nm; a first chromium bufferlayer overlying the first anti-reflection layer and having a thicknessof about 2 nm; an infra-red reflective layer of silver metal directlyoverlying the first buffer layer and having a thickness of about 95 nm;a second chromium buffer layer directly overlying the infra-redreflective layer and having a thickness of about 2.5 nm; and a secondanti-reflection layer of SnO₂ overlying the second buffer layer andhaving a thickness of about 39 nm; wherein, when the first heat-treatedglass substrate and the second heat-treated glass substrate each issubstantially clear soda-lime-silica glass having a thickness of about2.2 mm, the windshield has the following spectral properties: visiblelight transmittance greater than 75%; total solar energy transmittanceless than 50%; and total solar reflectance (IR region) of at least 25%.15. A heat-treatable coated glass article comprising a substantiallytransparent glass substrate with a substantially transparent coating ona surface of the glass substrate, the substantially transparent coatingcomprising: a first anti-reflection layer of dielectric materialoverlying the glass substrate, a first buffer layer overlying the firstanti-reflection layer, a first infra-red reflective layer of silvermetal directly overlying the first buffer layer, a second buffer layerdirectly overlying the infra-red reflective layer, a secondanti-reflection layer of dielectric material overlying the second bufferlayer, a third buffer layer overlying the second anti-reflection layer,a second infra-red reflective layer of silver metal directly overlyingthe third buffer layer, a fourth buffer layer overlying the secondinfra-red reflective layer of silver metal, and a third anti-reflectionlayer of dielectric material overlying the fourth buffer layer.
 16. Theheat-treatable coated glass article of claim 15 wherein each of theanti-reflection layers is SnO₂ and the buffer layers each is a chromiumbuffer layer.
 17. A motor vehicle windshield having low reflectance ofvisible light and high transmittance of visible light, comprising apolymer sheet sandwiched between a first heat-treated glass substratebent to a curved shape, a second heat-treated glass substrate bent to amatching curved shape, and a substantially transparent coating on asurface of at least one of the heat-treated glass substrates, thesubstantially transparent coating comprising: a first anti-reflectionlayer of dielectric material overlying the glass substrate, a firstbuffer layer overlying the first anti-reflection layer, a firstinfra-red reflective layer of silver metal directly overlying the firstbuffer layer, a second buffer layer directly overlying the infra-redreflective layer, a second anti-reflection layer of dielectric materialoverlying the second buffer layer, a third buffer layer overlying thesecond anti-reflection layer, a second infra-red reflective layer ofsilver metal directly overlying the third buffer layer, a fourth bufferlayer overlying the second infra-red reflective layer of silver metal,and a third anti-reflection layer of dielectric material overlying thefourth buffer layer.
 18. The motor vehicle windshield in accordance withclaim 17 wherein the polymer sheet is sandwiched between the concaveside of the first heat-treated glass substrate and the convex side ofthe second heat-treated glass substrate, the substantially transparentcoating being on the concave side of the first heat-treated glasssubstrate.
 19. The motor vehicle windshield in accordance with claim 17wherein the first and second anti-reflection layers are SnO₂, the bufferlayers are chromium buffer layers, the thickness of each chromium bufferlayer is 1 nm to 4 nm and the thickness of the infra-red reflectivelayer of silver metal is 6 nm to 13 nm, and wherein the windshield, whenthe glass is clear soda-lime-silica glass having a thickness of 2.2 mmto 3.5 mm, has the following spectral characteristics: visible lighttransmittance greater than 75%; total solar energy transmittance lessthan 50%; and total solar reflectance (IR region) of at least 25%. 20.The motor vehicle windshield in accordance with claim 19 wherein thefirst buffer and the second buffer have the same thickness.
 21. Themotor vehicle windshield in accordance with claim 19 wherein the firstbuffer layer has a thickness less than that of the second buffer layer.22. The motor vehicle windshield in accordance with claim 19 whereineach of the buffer layers is a chromium buffer layer.
 23. The motorvehicle windshield in accordance with claim 19 wherein the first bufferlayer is at least 1.5 nm thick.
 24. A method of manufacturing aheat-treatable coated glass article comprising a substantiallytransparent glass substrate with a substantially transparent coating ona surface of the glass substrate, comprising the steps of: providing asubstantially transparent glass substrate; and forming a substantiallytransparent coating on a surface of the substrate by: A) depositing afirst anti-reflection layer of dielectric material, B) subsequentlydepositing a first chromium buffer layer overlying the firstanti-reflection layer; C) subsequently depositing silver metal or coppermetal over the first chromium buffer layer to form a first infra-redreflection layer, D) subsequently depositing a second chromium bufferlayer directly onto the infra-red reflective layer, and E) subsequentlydepositing a second anti-reflection layer of dielectric material overthe second buffer layer to form a second anti-reflection layer.
 25. Themethod of manufacturing a heat-treatable coated glass article accordingto claim 24 wherein the first anti-reflection layer is depositeddirectly onto the surface of the glass substrate.
 26. The method ofmanufacturing a heat-treatable coated glass article according to claim24 wherein the layers of steps (A) through (E) are deposited in thatorder by magnetron sputtering at a corresponding series of stationswithin a sputtering chamber as the glass substrate moves continuouslyfrom station to station within the sputtering station.
 27. The method ofmanufacturing a heat-treatable coated glass article according to claim25 wherein the substantially transparent glass substrate issoda-lime-silica glass and the method further comprises, subsequent tostep (E), bending the glass substrate in tandem with a second glasssubstrate.